Right now you can get a United airlines mileage card that promises "up to" 40,000 free bonus United miles. If you qualify and buy enough in the year then you can get 40,000 miles. Thats a lot of miles. In my mind I first though, "hmm that should be enough to fly to Europe and save like $1000". So my first impression is that the bonus miles offered are worth roughly $1000 in airline tickets.
But what are those miles really worth? It depends on what the cost of the airline tickets are, where you fly and how many miles it costs to get the ticket in question. I decided to do some quick searches to get a rough idea of the value of airline miles for a couple airlines.
I searched for flights from the West coast to Dublin. One stop was about $927 whereas two stop flights was only $3 cheaper at $924. Of course I'd pay an extra $3 to avoid a stop. United flights only had options with 2 stops and the miles were 30,000 each way for 60,000 miles total. This makes the exchange of United miles versus cash to 60,000 miles = $924 cash. Therefore 1 mile = 1.54¢
Looking at a flight to Atlanta from the West coast next I find that with a bit of flexibility on dates that 37,500 United miles can get me a flight. If I'm not flexible then it would cost 50,000. Buying a ticket would be about $375 and shopping around for dates would only save maybe $10 as far as I saw. If I'm flexible with my dates then 37,500 United miles = $375 but if I'm not flexible then 50,000 miles = $375. Therefore flexibility means 1 mile = 1¢ but inflexible causes 1 mile = 0.75¢.
I can find a flight to Vegas for 25,000 United miles without too much hunting. On Orbitz the flights start around $160. This exchange makes the miles = 0.64¢.
So from my quick sample of 3 cities I get rough value for the United miles as follows:
United Miles
International = 1.54¢
Cross Country = 0.75¢ or 1¢
Local = 0.64¢
I did similar searches for Alaska Air as well. The miles were fairly similar for flights to Las Vegas or Atlanta. The flight to Dublin was harder to find and cost much more for some flights.
Alaska Miles
International = 1¢ to 1.54¢
Cross Country = 0.93¢ or 1¢
Local = 0.64¢
I picked United and Alaska to do my quick searches since I have the most miles with those airlines. If you've got a lot of miles with a specific airline then you might want to do a couple quick searches to check out availability for flights to cities you commonly fly to or would like to fly to. That will give you an idea what your miles are worth. If you're ever considering signing up for an airline miles rewards credit card like the United card I mentioned at the start, then you should definitely figure out how much the miles are worth and how easy it is to get the flights you'd want.
Bottom Line : The dollar value of airline miles will vary and depend on where you fly. For my quick searches I found values from 0.64¢ to 1.54¢ per mile.